Panel displays are developed rapidly since it is ultrathin in thickness and has energy-saving characteristics. Most of panel displays adopt shift registers. At present, not only the shift registers implemented by a Gate on Array (GOA) method can be integrated on a gate driving integrated circuit (IC), but also a process step for manufacturing a panel display can be reduced, so that cost of the panel display can be saved. Therefore, in recent years, the GOA technology is widely used in the process for manufacturing the panel display.
As shown in FIG. 1, it is a present GOA design scheme, a shift register on a gate driving circuit includes a plurality of shift register units S/R(1), S/R(2), S/R(3), . . . , S/R(N) being layered and in a cascade connection. Each of the shift register units S/R(n) (1≦n≦N) outputs a scanning signal via its own signal output terminal Output to a corresponding gate line G(n), a reset signal input terminal RST of S/R(n−1) and a signal input terminal InPut of S/R(n+1), and the scanning signal functions as resetting S/R(n−1) and starting S/R(n+1) respectively, wherein S/R(1) receives a frame start signal STV via its own signal input terminal.
Each of the shift register units receives a first supply voltage VSS and a second supply voltage VDD via a first supply voltage input terminal and a second supply voltage input terminal, respectively. Each of odd numbered shift register units receives a clock signal CLK via a clock signal input terminal CLK/CLKB, and each of even numbered shift register units receives a clock signal CLKB via a clock signal input terminal CLK/CLKB, said CLK and CLKB have phases opposite to each other.
A schematic internal structural diagram for said S/R(n) is as shown in FIG. 2.
An signal output terminal of S/R(n) outputs a scanning signal under the control of the scanning signal outputted from S/R(n−1) and the clock signal inputted from its own clock signal input terminal, that is, only a forward scanning for gate lines can be implemented from G(1) to G(N). However, in an actual application, a forward scanning may be required at some times, and a reverse scanning may be required at other times (that is, scanning from G(N) to G (1)), so the shift register in the prior art can not satisfy the actual requirements, that is; the shift register in the prior art has a problem of incapable of achieving a bi-directional scanning (that is, forward and reverse scanning).